The invention concerns a vehicle transmission.
Vehicle transmissions constructed in the countershaft gear train mode, from a standpoint of design and price, are very favorably looked upon as a selection for installation. These transmissions, as a rule, possess both an input and an output drive shaft, as well as a counter drive shaft parallel to the said shafts. The flow of force is conducted over a first gear set from the input drive shaft onto the counter shaft, and from there, by means of a second gear set to the output shaft. One of the said gear sets, which takes part in all gears and is known as a xe2x80x9cconstantxe2x80x9d, possesses two fixed gears, which mesh together and are seated at any given time on the counter shaft, the input shaft or the output shaft. The other gear set possesses an idler gear and a fixed gear. This set is normally assigned to one gear stage. The gear set for reverse action, i.e., the reverse gearing, possesses an intermediate gear, which, first, meshes with the idler gear and second, with the fixed gear, and thus the direction of rotation of the output shaft as opposed to the input shaft is reversed.
For the direct through-drive, unimpeded through the transmission, which corresponds to a gear ratio of one, the input drive shaft is coupled, by means of a shift-clutch directly with the coaxially aligned output shaft, without carrying any torque by means of gear sets. In this case, a vehicle transmission, that has six forward drives, of which one serves as a direct gear, and with one reverse gear requires six gear sets and seven shifting clutches. The shifting clutches in the vehicle transmission, as a rule, are of such design that they can be activated, one after the other, by the driver through mechanical activation elements, since the driver operates a manual shift lever in two mutually perpendicularly arranged planes of motion.
By means of a movement in the first motion plane, two gears of a shift sequence are selected, and by means of a movement in the second motion direction another of the chosen gears is shifted. In order to be able to drive a vehicle motor during travel in an optimal operational zone, transmissions with many gear stages are desirable, whereby the stage jumps between the individual gears, from the highest to the lowest gears, should progressively climb from the highest gear to the lowest gear. What is achieved by this is, that the driver, by a fine incrementation of the speed of rotation of the vehicle motor, can very well suit the vehicle speed. Further the entire gear ratio range of the vehicle transmission, between the first and the highest gears should be large, whereby the ratio of the gear ratio range to the number of the gear stages is relatively large and expense can be held at a minimum. Such vehicle transmissions permit, at a justifiable expense, the use of up to six forward gear stages.
The cost of construction of a vehicle transmission can be reduced, in that some gear sets can be employed in multi use, in which they are put to use for the formation of different gear stages. By way of example, in the case of the group drives of a principal gear-drive group, an auxiliary gear-drive group, consisting of two or more gear sets is installed either leading or trailing, so that from the combination of the gear sets of the auxiliary gear-drive groups with the gear sets of the principal gear-drive groups, the number of the gear stages of the vehicle transmission can be obtained from the product of the number of the gear stages of the individual drive groups. The gear stage jumps between the gear sets of the auxiliary gear-drive group are so attuned to the stage jumps between the gear set groups of the principal transmission, that, all in all, there is created a useable gear staging of the vehicle transmission. Because of the group assembly mode of the vehicle transmission, in general, only a geometric, but not a progressive staging of the entire gear ratio range is possible, since, by the multiple use of the gear sets of the principal gear-drive group, the stage jumps of the said principal gear-drive repeat themselves multiple times.
The auxiliary gear-drive group is, as a rule, so designed, that, operating as a so-called split transmission group, it subdivides the stage jumps of the principal gear-drive group or functions as the so-called range drive group, and extends the ratio range of the principal gear group upward or downward. While the principal gear group, as a rule, is laid out in such a manner, that it can be shifted manually with mechanical means, the auxiliary gear-drive group is activated by outside force, i.e., electrical, hydraulic, or pneumatic. Such group transmissions are known for drives with eight and more gears as described in xe2x80x9cConstruction Book Vol. 26, Loomann, xe2x80x9cToothed Gear Transmissionsxe2x80x9d, 1970 Springer Verlag, Berlin, pages 181, ff.
DE 42 05 670 C1 disclosed a vehicle transmission constructed in accord with the auxiliary assembly mode, in which, with five gear sets, a total of six forward gears, including one direct gear, and one reverse gear have been realized. This is brought about, in that an centrally placed gear set is in multiple use, since the said gear set can be connected for one thing, to the input drive shaft, and for another, to the output drive shaft. The number of the gears can, when desired, be increased by two gears, by adding one additional gear set. This kind of a xe2x80x9cwrap-aroundxe2x80x9d transmission does not permit itself to be shifted in a logical shift pattern by customary mechanical hand shift apparatuses. In any case, this is not an obstructive condition, as the clutch for shifting can be activated by external power means.
The purpose of the invention is to create a vehicle transmission with nine forward gears and one reverse gear, with said transmission having a low manufacturing cost.
In accord with the invention, in the case of the vehicle transmission, between the input drive shaft and the output drive shaft is placed a coaxial intermediate shaft. This intermediate shaft can be engaged by means of a first shifting clutch with the input drive shaft, and by a sixth shifting clutch with the output shaft. The counter shaft is subdivided into a first counter shaft and into second, counter shaft, placed coaxial to the first, which can be engaged with the first counter shaft by means of a second shifting clutch. The first to the third gear set and the reverse set form a principal gear-drive, whereby a first fixed gear of the first gear set is seated on the input drive shaft and meshes with a first idler gear on the first counter shaft. A second, fourth and seventh fixed gear of the second and third gear set, as well as the reverse gear set are seated on an intermediate shaft, wherein the second fixed gear meshes with a third fixed gear on the first counter shaft while the third fixed gear drives a second idler gear and the seventh fixed gear, by means of an intermediate gear, drives a fifth idler on the second counter shaft. The fourth and fifth gear sets, which form a range group on the output side, possess a fifth fixed gear, respectively, a sixth fixed gear on the output drive shaft, which mesh with the idler gears on the second counter shaft.
With the aid of an appropriate shifting logic, it now becomes possible to realize the construction of a vehicle transmission with nine shift stages at the same manufacturing cost of a vehicle transmission in the group construction mode having six shift stages. This makes possible both smaller gear shift jumps and a greater spread of the vehicle transmission. By means of the multi-use of some gear groups, the possibility exists that a total of six gear sets and eight shift-couplings will suffice. These must all, in any event, be shifted by external forces, which, in this day of the actuator technology presents no particular difficulty. Because of this fact, such transmissions can be equipped in a simple manner to bring about automatically shifting vehicle transmissions.
An advantageous shifting logic arises, when, for the formation of a first to a fourth gear stage, the flow of force is directed through the fourth gear set, and for the formation of a fifth to eighth gear stage, the flow of force is directed through the fifth gear set. Besides this, the flow of force in the first and fifth gear set is led over the third gear set, in the second and sixth gear set, through the second gear set, in the third and seventh step, through the first gear set, and in the fourth and eighth through the first, second and third gear set. In a ninth, direct gear position, the input drive the input drive shaft, by means of the intermediate shaft, and by the first and second shifting clutches is connected to the output shaft. A reverse gear position, is advantageously fashioned, in accord with a desired gear ratio, through the reverse gear set and the fourth or fifth gear set, through which the flow of force is conducted.
With advantageous gear ratios, the gear sets, for example, for the first gear set about 1.38, for the second gear set a value of 2.39, for the third gear set, 3.15, for the fourth gear set 0.35 for the fifth gear set 1.05 and for the reverse gear set of 2.90, there is a transmission spread of 9.00 between a transmission ratio in the first gear position of 9.00 to a transmission ratio of 1.00 in the ninth gear. Thus the gear stage jump, between the individual steps is geometric with a factor of about 1.31.